如何用javascript改变<bgsound scr=".....">里的scr的值

1<bgsound id="bgsound"/>

1<a href="1.mid" onclick="bgsound.src=this.href;return(false)">A</a>

1<br/>

1<a href="2.mid" onclick="bgsound.src=this.href;return(false)">B</a>

1<bgsound id="snd" loop="-1" src="music1.mid" volume="0"/>

1<a href="javascript:snd.src='music1.mid'">第1首歌</a>

1<a href="javascript:snd.src='music2.mid'">第2首歌</a>

1<a href="javascript:snd.src=''">停止</a>

1<a href="javascript:snd.volume=-100000">静音</a>